NYCDEPCostAnalys isReport-0607 .pdf - New York-New Jersey ...

1.1.10 Membrane Bioreactors
Figure 1-7: FSBNR-DF Process Configuration
Membrane Bioreactors (MBR) are a combination of activated sludge reactors and membrane
filtration facilities. Membrane facilities replace the clarification process by a physical barrier
that separates solids from the liquid phase within the wastewater. Because the MBRs replace the
clarifiers and provide a physical barrier, the aeration tanks can be operated at higher mixed liquor
concentrations (approximately 8,500 mg/L) than conventional activated sludge systems. This
allows for reduced tank sizes when compared to other activated sludge processes. The
membranes used for this process are similar to the membrane filtration process, but they are
operated at much lower flux rates (flow per unit) to handle the significantly higher solids loading
rates.
The process involves modification of the existing step aeration process to allow the entire flow
stream to the head of the first pass. Zones will be created to allow the cycling of oxic and anoxic
zones that are necessary to remove nitrogen. The process will require baffle walls to separate the
oxic and anoxic portions of the tank. Mixers will be required in the anoxic zones to keep solids
in suspension and prevent the formation of stagnant zones. The process will include the
installation of fine screening, recirculation pumping, RAS pumping, and the construction of new